Devices that reflect selected wavelengths of light are well known and have been in use for many years. In typical configurations, a reflector is formed by depositing alternating layers of dielectric materials on a substrate. For example, alternating layers of a first dielectric material having a high index of refraction with a second dielectric having a low index of refraction, wherein the alternating layers have a fixed thickness, can produce a reflector that reflects light in the visible spectrum in a pattern that has a single peak intensity. A similar structure that uses two equal thickness dielectric layers separated by a metal layer similarly can result in a reflector that reflects visible light in a pattern that has a single peak intensity (see, for example, U.S. Pat. Nos. 5,214,530 and 6,262,830).
Conventional reflectors, however, can have physical and optical limitations that prevent their use in some applications. For example, alternating dielectric reflectors can have a total layer thickness on the order of 1.5 microns. Furthermore, single peak reflectors may lack the optical qualities that are desirable for some applications—for example, viewing screens that are used for image projection devices.
What are needed in the art are improved optical reflectors that are relatively thin, relatively simple and inexpensive to manufacture, and that provide desirable reflection within the visible spectrum.